Osteopathic lymphatic pump treatments (LPT) have been advocated for the treatment of infectious disease, and in particular pneumonia, but with no firm scientific foundation. Our preliminary experiments have shown that LPT increases thoracic duct lymph flow and leukocyte concentrations in both rats and dogs. Thus, these initial results support our hypothesis that LPT increases the mobilization and redistribution of leukocyte pools, which may enhance immune surveillance and strengthen host defenses against infection. The proposed investigation will test this hypothesis by accomplishing the following Specific Aims: 1) Determine the tissue source of leukocytes released into lymph and blood during LPT, 2) Determine the distribution of LPT-mobilized leukocytes in peripheral tissues, and 3) Determine if LPT enhances immunity and protection against pulmonary infection. The experiments in Specific Aims 1 and 2 will be conducted in both conscious and anesthetized surgically instrumented dogs. The experiments described in Specific Aim 3 will be conducted in rats. Thoracic duct lymph flow will be measured with an implanted transducer and sampled through an indwelling catheter. Lymph and blood will be collected to determine the regional release of leukocytes and their uptake from blood during LPT. The contribution of the spleen and mucosal tissue will be determined by in situ fluorescently labeling of tissues. Reappearance of labeled leukocytes in lymph will index the repopulation rate of lymph sources sensitive to LPT. Measurements of the rate of appearance and disappearance of leukocytes in blood will be made to determine 1) if leukocytes are released directly into the circulation, particularly from the spleen and gut associated lymphoid tissues, and if LPT may increases this release, and 2) if LPT enhances the return of mobilized leukocytes to tissues. To determine if LPT enhances immunity and protection against pneumonia, rats will be nasally infected with Streptococcus pneumoinae bacteria. We hypothesize that rats receiving LPT will have reduced lung bacteria. To quantify and characterize leukocytes in lymph, blood and tissue, the following analyses and procedures will be used: differential cell counts, flow cytometry, enzyme-linked immunosorbent assay (ELISA), enumeration of antibody forming cells by enzyme-linked immunospot (ELISPOT), and fluorescent labeling of leukocytes. The information gained from this novel investigation will provide a robust scientific basis and rationale for the use of LPT to enhance immunity and treat infection. In addition, this new information will expand basic understanding of the lymphatic system and its role in immunological function. PUBLIC HEALTH REVELANCE: In this proposal we will test the hypothesis that LPT increases the mobilization and redistribution of leukocyte pools, which would enhance immune surveillance and strengthen host defenses against infection. The information gained from this novel investigation will provide a robust scientific basis and rationale for the use of LPT to enhance immunity and treat infection. In addition, this new information will expand basic understanding of the lymphatic system and its role in immunological function.